US3731057A

US3731057A - Sensing means for electric fan heater

Info

Publication number: US3731057A
Application number: US00154778A
Authority: US
Inventors: R Kunz; A Schulz
Original assignee: GEC BRIDGEPORT
Current assignee: GEC BRIDGEPORT; GEC BRIDGEPORT US
Priority date: 1971-06-21
Filing date: 1971-06-21
Publication date: 1973-05-01
Anticipated expiration: 1990-05-01

Abstract

An electric fan heater of the space heating type includes a housing having an air inlet opening in the top wall and an air outlet opening in the front wall with an electric heating element in close proximity thereto. A motor driven axial flow fan having a vertical axis of rotation is utilized to provide an air flow through said housing between said inlet and outlet openings. A temperature responsive safety switch is located above the heating element and is positioned in an air flow passage having one end in air flow communication with the air outlet and its other end in air flow communication with the air outlet and its other end in air flow communication with the inlet side of the fan whereby heated air is allowed to flow back to the fan over the safety switch in the event of an obstruction at the outlet opening. In one embodiment a shielding member is provided between the air inlet opening and the fan to partially block the inlet opening. The shielding member is positioned above the fan adjacent the centrifugal air stream path toward the front wall and overlies the air passage.

Description

May 1,1973

1/1967 Switzerland... ......................219/370 SENSING MEANS FOR ELECTRIC FAN HEATER Primary Examiner-A. Bartis [75] Inventors: Raymond W. Kunz, Monroe; Albert Atz0rneyLawrence R. Kempton et a].

E. Schulz, Fairfield, both of Conn.

[73] Assignee: General Electric Company, Bridgeport, Conn.

June 21, 1971 Filed:

wall and an air outlet opening in the front wall with an electric heating element in close proximity thereto. A

App]. No.: 154,778

motor driven axial flow fan having a' vertical axis of rotation is utilized to provide an air flow through said housing between said inlet and outlet openings. A

[52] US. Cl. ....................219/363, 34/243 .H05b l/02,

219/364, [51] Int.

temperature responsive safety switch is located above [58] Field of Search the heating element and is positioned in an air flow passage having one end in air flow communication with the air outlet and its other end in air flow communication with the air outlet and its other end in air flow communication with the inlet side of the fan whereby heated air is allowed to flow back to the fan [56] References C'ted over the safety switch in the event of an obstruction at UNITED STATES PATENTS the outlet opening. In one embodiment a shielding member is provided between the air inlet opening and ed Mhn e a i mm m eCw at Tmn o m w m .1 e r m h w p .I 0 m F flea m vw i .m o w 10'. 3 ea r h h ke mm 6, 1.1 g bhmm m ses i WO a h .mpmp C H.Br.. a m 5 r pel o u wniw m nfl e eV t.mCO 7 39 7 69 03634 33 3 9 99 2 .1

ML mm m dm ew.m n muw w p810 erwr JB B 76375. 656336 999999 l l l 1 ll 26 59 5729 62895 67572 v x a 1 a 9 FOREIGN PATENTS OR APPLlCATlONS 1,074,432 7/1967 GreatBritain....................,..;219/370 Patented May 1, 1973 s Sheets-Sheet 1 J? ll le SENSING MEANS FOR ELECTRIC FAN HEATER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to electric space heaters, and more particularly to portable electric fan heaters utilizing a fan propeller for producing a flow of air through the heater.

2. Description of the Prior Art Electric space heaters utilizing a fan propeller to produce an air flow through the heater are quite common. Some of these fan heaters utilize a direct flowthrough arrangement wherein air is drawn into the rear of the heater housing by rotating blades and then through a suspended heating element to heat the air, then out an opening at the front of the heater. Some electric fan heaters are arranged so that air is drawn in at the bottom of the front of the fan heater, then around a reflector that heats the air and expelled from the fan heater at the top of the front wall. Some electric fan heaters are arranged so that the propeller of an axial flow fan draws air into the heater through the top panel or wall and then out through a front wall thus requiring the air to make a right angle turn within the heater from the inlet to the outlet. In such an arrangement the heating element is normally located near the outlet opening of the fan heater. Itis this later electric fan heater arrangement to which this invention applies particularly.

In fan heaters it has been common practice to provide safety tip-over switches to interrupt the supply of electrical current to the heater when it is not in a normal upright position. Moreover, some heaters also utilize another safety arrangement that will interrupt the electrical currentto the heater in the event the air outlet opening of the heater is placed too close to other objects, such as walls or curtains, thus causing an excessive heat condition that could be hazardous. Moreover, if the housing of the fan heater is to be molded plastic, which is desirable both from an economical and appearance standpoint, such a'safety arrangement needs to be reliable and quickly responsive to temperature rise that could otherwise deform or melt the plastic housing. This invention relates to an electric fan heater utilizing an axial flow fan that has an improved safety arrangement that operates to interrupt the electrical current to the fan heater when the air outlet opening is close enough to an obstruction to cause an excessive temperature rise in the fan heater.

SUMMARY OF THE INVENTION In accordance with this invention, there is provided an electric fan heater that includes a housing having a top, sides, bottom, rear and front walls with an air intake opening in the top wall of the housing and an air outlet opening in the front wall. Between the inlet opening and outlet opening is an electric motor-driven axial fan having a bladed propeller with a vertical central axis of rotation which, upon rotation, provides an air flow through the fan heater from the inlet to the outlet. A heating element is positioned in the air flow close to the air outlet opening at the front of the housing. A temperature responsive switch is located in a thermal sensing position above the heating element and an air passage means is provided between the temperature responsive switch and the inlet side of the axial fan.

It is an object of this invention to provide an improved electric fan heater.

It is also an object of this invention to provide an improved electric fan heater utilizing an axial flow fan propeller wherein thermal safety means are provided for sensing an excessive temperature rise due to the proximity of an obstruction near the outlet opening that restricts the free flow of air from the fan heater.

It is another object of this invention to provide an electric fan heater having a plastic molded housing and utilizing an axial flow fan propeller that draws air in through an opening in the top wall and out a front wall opening wherein the close proximity of an obstruction in front of the front wall causes an excessive temperature rise to be sensed by a temperature responsive switch which deenergizes the fan heater.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the electric fan heater with a broken-away portion showing the location of the return air passage.

FIG. 2 is a perspective view of the electric fan heater with the housing opened up to show the internal construction of the fan heater.

FIG. 3 is a front elevational view in cross section of the fan heater.

FIG. 4 is a side elevational view in cross section of the fan heater.

FIG. 5 is a schematic diagram showing the electric circuit of the electric fan heater.

FIG. 6 is a perspective view of an alternate embodiment of the fan heater.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, there is illustrated in FIGS. 1 and 2 a portable electric fan heater, generally shown at 10 and including a case or housing 11. The housing 11 is illustrated as a rectangular housing having a top wall 12, a bottom wall 13, a front wall 14, a rear wall 15, and

side walls

16a and 16b. The housing is molded from plastic material and made in two parts, a top half 17 and bottom half 18. Formed in the top wall 12 is a circular inlet opening 20 which has a protective grid 21 covering the exterior portion of the opening. Directed downwardly from the periphery of the inlet opening 20 is a circumferential cylindrical depending wall 22.

Mounted on the bottom wall 13 of the housing and located to one side of the housing is a fan assembly 23 having an electric motor 24 that rotates fan propeller 25 on a vertical central axis. The fan propeller 25 and the inside diameter of the depending wall 22 are dimensioned so that when the top 17 and bottom 18 of the housing are closed, as shown in FIG. 1, the fan propeller will be withinthe depending wall 22. The front wall 14 of the housing has an exit or outlet opening 30 that extends substantially the length and height of the front wall. The outlet opening 30 is covered by a protective grid 31 that is retained in place by any suitable means on the front wall. Behind and in close proximity to the outlet opening 30 is an electric resistance heating wire assembly 32 consisting of a rectangularshaped box 33 formed of electric insulating material, such as mica board, around which is strung a coiled resistance wire 34, which resistance wire when electrically energized provides the source of heat for heating the flowing air.

A control section 35 is provided in the top wall 12 of the housing and located on the opposite side of the interior of the housing from the fan assembly. The control section 35 contains a high and low temperature selection switch 40 for energizing and de-energizing various portions of the heating wire, which will be discussed later in connection with FIG. 5. The control section also has an adjustable thermostat with a knob 41 accessible to the user for adjusting the operation of the fan heater to give the desired temperature level. It will be noted from FIGS. 1 and 2 that the construction of my fan heater is quite simple in that the housing is formed in two plastic molded parts, a top half 17 and a bottom half 18. A partition 37 to one side of the heater wire assembly 32 and another partition 38 on the opposite side are molded into the bottom half 18 and are utilized to direct the air through the heating wire assembly 32. A top partition 39 for the same purpose is molded into the top half 17. Within the fan heater there is also only an electric motor-driven axial flow fan for producing an air flow through the heater, a heating wire assembly for heating the air as it is flowing through the fan heater and necessary electrical wiring. The electrical wiring for energizing the motor and controlling the operation of the fan heater will be discussed later in connection with FIG. 5.

With reference to FIGS. 1 4, it is shown that in the electric fan heater there is provided a fan arrangement utilizing a generally axial flow fan having a propeller with a plurality of blades. In this arrangement the in- 7 take opening to the fan is defined by a depending circumferential wall 22 and is so mounted that it surrounds at least the intake or upper portion of the fan.

By upper portion it is meant that portion above a central horizontal plane through the propeller. Means are provided for effecting a pressure rise in the output flow from the fan-These means comprise the bottom wall 13 positioned directly below and spaced from the output side of the fan propeller, which bottom wall is used for diverting radially the output flow from the propeller, and a chamber formed by the fan heater housing surrounding the forward portion of the fan propeller (below the central horizontal plane). The chamber contains a body of free air and collects therein the radial flow effected by the bottom wall 13. Upon rotation of the fan propeller, air pressure is effected due both to centrifugal forces setup as a result of the radial outward and circular movement of the air flow, and to a free stream diffusion process occurring as the air flow passes through the area between the bottom wall 13 and the depending wall 22. Because of its change in radial direction, the air flow is directed away from the center of the fan and prevented from return in recirculation therethrough. The recirculation would otherwise normally occur because the center of the fan is weak whereas the peripheral area of the fan moves 75 percent of the air, which air is thrown forwardly from the tips of the blades and is thus the strong" portion of the propeller. After the air has increased in pressure, the flow is then discharged from beneath the rotating fan propeller following a path of least resistance to the opening 30 in the front wall of the housing.

To explain the pressure rise caused by an axial flow fan in somewhat simpler language it may also be described as follows: one pressure rise is effected by the decrease in velocity of the axial air flow from the fan as it is converted to radial flow by the interference of the bottom wall of the housing; and a second pressure rise is effected by the decrease in velocity of the radial flow as its centrifugal forces are resisted by the adjacent free air in the exhaust area of the chamber. A conventional axial flow propeller fan is utilized in this invention because no appreciable static pressure is required in order to create an air flow, but yet it delivers a large volume of air through the fan heater. Moreover, a propeller fan is inexpensive and occupies much less space than other types of air pressurizing means.

With particular reference to FIGS. 1 4, air is drawn into the fan heater through inlet opening 20, pressurized, as described previously, by the fan propeller located to one side of the heater housing then leaves the area below the fan propeller in a centrifugal air flow path via an exhaust channel at the other side of the housing from the fan propeller as this is the path of least resistance. The air flow path from the fan propeller 25 to the outlet opening passes through the heating wire assembly 32 which consists of an elongated rectangular-shaped box 33 formed of electric insulating material, such as mica board, around which is strung a coiled resistance wire 34. The heater wire runs are spaced from each other to allow the air to flow readily through the heating wire assembly. It will be noted from FIG. 3 that the heating wire assembly 32 is quite wide and covers an extensive area across the front wall of the fan heater. Also, the heating wire assembly 32 is off center of the heater housing toward the centrifugal air flow path and is below the central horizontal plane of the fan propeller.

It is common practice in electric heaters to provide a combination thermostat and tip-over switch. The thermostat portion of the switch operates to de-energize the heating element responsive to adjustable temperature limitations built into the thermostat. The thermostat is normally positioned so that a knob is accessible to the user to control the heat output of the heater. The tip-over portion of the switch combination is utilized to interrupt the supply of current to the heater in the event the heater would fall on its face and cover up the outlet opening thereby causing a dangerously high accumulation of heat. In addition, as a safety factor, a temperature responsive switch can be positioned in close proximity to the heating wire assembly to sense any abnormally high temperature caused by a malfunction of the heating wire assembly. The temperature responsive switch senses the excessive heat and will deenergize the fan heater until the correct temperature level is once again achieved. As shown in FIGS. 3 and 4, the temperature responsive switch assembly 42 includes a base 43 upon which are mounted the various electrical contacts and lead connectors separated by ceramic insulator washers 44. The temperature responsive switch assembly is so constructed that contact blade 45 is in contact with contact blade 46 through contact buttons carried by each blade. Contact blade 46' is spring biased so that it is normally in contact with blade 45 and an adjusting screw 47 is provided to adjust the contact tension during the initial calibration of the temperature responsive switch assembly. Also in the switch assembly is a thermally responsive bimetalic blade 48 that operates in the usual fashion. When the bimetalic blade is subjected to heat, the difference in co-efficient of expansion of the two laminated metals from which the blade is made causes the blade to bend. Bimetalic blade 48 carries an elongated button 49 that extends upwardly to contact blade 45. When'the temperature is elevated bimetalic blade 48 bends gradually and with the metal having the lower co-efficient of expansion on the side of the elongated button 49, blade 48 bends toward contact blade 45 and when sufficient force is exerted the contact blades are separated thus interrupting the electrical current to the fan heater.

Above and behind the heating wire assembly 32 is downwardly directed wall 39 molded into top half 17 of the housing. This wall is utilized along with

partitions

37 and 38 to prevent the air flow from escaping from within the housing without going through the heating wire assembly. Directly behind the temperature responsive switch assembly 42 is a cutout section 51 with another cutout section 52 also provided in depending wall 22. Joining these two cutout sections are side walls 53 that cooperate with the cutout sections to provide an air passageway from the temperature responsive switch assembly 42 to the upper or inlet side of the fan propeller. By this internal arrangement the air flow is as shown by arrows designated a in FIG. 4. The air comes into the fan heater through inlet opening 20 and is drawn down through the propeller 25 where it is pressurized and flows out through heating wire assembly 32 to outlet opening 30 in the front wall 14 of the housing 11 and expelled from the fan heater. In the event the opening 30 is in close proximity to a vertical obstruction, such as a wall or a curtain, the expelled outwardly flowing heated air hits the obstruction and is forced back into the top portion of the opening 30 where it sweeps across the temperature responsive switch assembly 42. The expelled air flows in this path because behind the temperature responsive switch assembly there is provided the previously described air passageway to the inlet side of the fan propeller that affords a path of least air resistance. By this arrangement then, the temperature responsive switch assembly 42 can perform two functions; namely, it can be used as a safety switch for an overtemperature condition of the heating wire assembly should it malfunction and it can also sense an excessive temperature rise due to an obstruction in front of the air outlet opening. In addition to providing these dual safety functions for the single temperature responsive switch assembly, the above described arrangement also permits the desirable use of a plastic housing for the fan heater. The temperature responsive switch can now quickly and accurately detect a temperature level calibrated into the switch so that it will de-energize the fan heater before the temperature rise is sufficient to deform or melt the plastic housing.

For a description of the electrical circuit of the fan heater and a more detailed discussion of its operation, reference is made to FIG. 5. Conductor 54 of the line input from power cord plug 56 is connected to adjustable thermostat 55 that has an off" position. The adjustable thermostat 55 has a control knob 41 so that the user may adjust the thermostat to the desired temperature level setting as well as turning the fan heater on and off. Conductor 57 connects the adjustable thermostat 55 through junction 63 to fan motor 24. Fan motor 24 is connected to temperature responsive switch asble thermostat 55 by conductor 62 through heat selection switch 40, junction 66, conductor 61, junction 63 and conductor 57. With the foregoing electrical circuit, the following operation will be provided with the power cord plug 56 inserted into a wall receptacle. When the adjustable thermostat is in the off position, neither the fan motor nor any of the heating elements are energized. With the adjustable thermostat turned on and switch 40 open to provide low heat, a closed circuit is completed such that fan motor 24 and the heater element segments 34a and 34b are energized. The circuit completed is from power cord plug 56 through conductor 54 to adjustable thermostat 55, conductor 57, junction 63 to electric motor 24 and from motor 24 through conductor 58, junction 64, conduit 67 to temperature responsive switch assembly 42 back to the other side of the line 59. The circuit also includes heater segments 34a and 34b by providing the additional circuit from adjustable thermostat 55 through conductor 57, junction 63, conductor 61, junction 66, through parallel heating wire segments 34a and 34b, conductor 60 to junction 64. Upon closing switch 40 for the high heat output the above described circuit also will now include heating wire segment 34c. That additional portion of the circuit is from junction 66 through conductor 62 via closed switch 40 to heating wire segment 340 to junction 64. As can be seen, the temperature responsive switch 42 is placed in the circuit such that if an excessive temperature rise occurs it will respond to open the circuit and de-energize all the heating wire segments and the fan motor.

FIG. 6 shows an alternate preferred embodiment of the fan heater. The fan heater is basically the same as described above except that in addition a shielding member 65 is shown partially blocking the air inlet opening 20. By locating the shielding member above the fan propeller 25 and adjacent the centrifugal air stream path toward the front wall there is provided a reduced air pressure zone beneath the fan propeller directly below the shielding member 65. By having the passageway leading back to the inlet side of the axial fan beneath the shielding member 65, good recirculation air flow characteristics are accomplished.

The foregoing is a description of the preferred embodiment of the invention and variations may be made to the apparatus without departing from the spirit of the invention, as defined in the appended claims.

We claim:

1. An electric fan heater comprising:

a. a housing, said housing having top, bottom, side,

rear and front walls,

b. an air inlet opening in the top wall of the housing,

0. an air outlet opening in the front wall of said housd. a motor-driven axial fan within the housing between the inlet and outlet openings,

e. a heating element'located between the air outlet and fan in close proximity to the air outlet open ing,

' f. a temperature responsive switch for de-energizing the fan heater, said switch positioned above said heating element,

g. air passage means between the temperature responsive switch and the inlet side of the fan, one end of said air passage in air flow communication with the inlet side of the fan and the other end in air flow communication with the air outlet and located above the heating element said temperature responsive switch being in the path of air flow through the air passage means, and

h. said air inlet opening having a depending circumferential wall extending below the central horizon tal plane of the fan. propeller and having a cut-out portion to accommodate the air passage means between the temperature responsive switch and the inlet side of the fan.

An electric fan heater comprising:

a. a housing, having top, side, rear, bottom and front walls,

. an air inlet opening in the top wall of the housing,

c. an air outlet opening in the front wall of the housa motor-driven axial fan propeller within the housing, said fan having a vertical central axis of rotation to thereby provide a centrifugal air stream path within the housing in the direction of the air outlet opening,

e. a heating element in-said air stream path between the air outlet and fan propeller and located in close proximity to the air outlet opening,

f. a temperature responsive switch for de-energizingthe fan heater, said switch positioned above said heating element,

g. air passage means between the temperature responsive switch and the inlet side of the fan, one end of said air passage means in air flow communication with the inlet side of the fan and the other end in air flow communication with the air outlet and located above the heating element, said temperature responsive switch being in the path of air flow through the air passage means, and

h. a shielding member between the fan propeller and air inlet opening to partially block the air inlet opening, said shielding member being located above the fan propeller adjacent the centrifugal air stream path toward the front wall and covering the air passage.

3. The electric fan heater of claim 2 wherein the air inlet opening has a depending circumferential wall extending below the central horizontal plane of the fan propeller and having a cut-out portion to accommodate the air passage means between the temperature responsecured to the top of the box to sense excessive tem-' perature rise in the heating element and also deflected heated air from the outlet opening caused by an obstruction at said opening.

Claims

1. An electric fan heater comprising: a. a housing, said housing having top, bottom, side, rear and front walls, b. an air inlet opening in the top wall of the housing, c. an air outlet opening in the front wall of said housing, d. a motor-driven axial fan within the housing between the inlet and outlet openings, e. a heating element located between the air outlet and fan in close proximity to the air outlet opening, f. a temperature responsive switch for de-energizing the fan heater, said switch positioned above said heating element, g. air passage means between the temperature responsive switch and the inlet side of the fan, one end of said air passage in air flow communication with the inlet side of the fan and the other end in air flow communication with the air outlet and located above the heating element said temperature responsive switch being in the path of air flow through the air passage means, and h. said air inlet opening having a depending circumferential wall extending below the central horizontal plane of the fan propeller and having a cut-out portion to accommodate the air passage means between the temperature responsive switch and the inlet side of the fan.

2. An electric fan heater comprising: a. a housing, having top, side, rear, bottom and front walls, b. an air inlet opening in the top wall of the housing, c. an air outlet opening in the front wall of the housing, d. a motor-driven axial fan propeller within the housing, said fan having a vertical central axis of rotation to thereby provide a centrifugal air stream path within the housing in the direction of the air outlet opening, e. a heating element in said air stream path between the air outlet and fan propeller and located in close proximity to the air outlet opening, f. a temperature responsive switch for de-energizing the fan heater, said switch positioned above said heating element, g. air passage means between the temperature responsive switch and the inlet side of the fan, One end of said air passage means in air flow communication with the inlet side of the fan and the other end in air flow communication with the air outlet and located above the heating element, said temperature responsive switch being in the path of air flow through the air passage means, and h. a shielding member between the fan propeller and air inlet opening to partially block the air inlet opening, said shielding member being located above the fan propeller adjacent the centrifugal air stream path toward the front wall and covering the air passage.

3. The electric fan heater of claim 2 wherein the air inlet opening has a depending circumferential wall extending below the central horizontal plane of the fan propeller and having a cut-out portion to accommodate the air passage means between the temperature responsive switch and the inlet side of the fan.

4. The electric fan heater of claim 3 wherein the housing is molded from plastic material and the temperature responsive switch is responsive to a temperature below a temperature at which the plastic material will be deformed.

5. The electric fan heater of claim 4 wherein the heating element is wound upon an electrically insulated heater box and the temperature responsive switch is secured to the top of the box to sense excessive temperature rise in the heating element and also deflected heated air from the outlet opening caused by an obstruction at said opening.